Fix for the NavigationControllerTest.BackSubframe test failures with PlzNavigate

content/test/test_render_frame_host.h

Index: content/test/test_render_frame_host.h
diff --git a/content/test/test_render_frame_host.h b/content/test/test_render_frame_host.h
index de3db0cc73311297106156b558daea0f11fc3939..af897746a8e31cc7eeceb95778f9e6f82b409ab5 100644
--- a/content/test/test_render_frame_host.h
+++ b/content/test/test_render_frame_host.h
@@ -21,6 +21,8 @@ struct FrameHostMsg_DidCommitProvisionalLoad_Params;
 
 namespace content {
 
+class PageState;
+
 class TestRenderFrameHostCreationObserver : public WebContentsObserver {
  public:
   explicit TestRenderFrameHostCreationObserver(WebContents* web_contents);
@@ -146,6 +148,11 @@ class TestRenderFrameHost : public RenderFrameHostImpl,
   // Creates a WebBluetooth Service with a dummy InterfaceRequest.
   WebBluetoothServiceImpl* CreateWebBluetoothServiceForTesting();
 
+  // Creates an encoded page state for the |url|, |item_sequence_number| and
+  // |document_sequence_number| parameters.
+  static PageState CreatePageStateForURL(const GURL& url,
+                                         int64_t item_sequence_number,
+                                         int64_t document_sequence_number);
  private:
   void SendNavigateWithParameters(int page_id,
                                   int nav_entry_id,